It is known to supply parenteral fluids to be administered intravenously in disposable plastic bags, as distinguished from the more conventional bottles, in varying quantities of 1 liter, 1/2 liter, 1/4 liter, and so on. However, such plastic bags, like the bottles which they have superseded to a degree, lack means other than known unsatisfactory clamp means for altering the calibre of the IV tubing line in which the bags are connected, for regulating the rate of fluid flow therefrom. That is to say, despite the need for simple, effective means for dispensing parenteral fluids from a plastic bag containing a supply thereof, up to the present time such need could be satisfied only by the use of electrically powered positive pressure pumps connected to the IV tubing line which are both expensive and cumbersome in use, such necessitating disconnection of the pump motor with the result that flow of the fluid is stopped until another electrical connection is reached. In other situations, it is desirable that the patients be ambulatory, walking halls as when receiving heparin, with the result that the patient's walking is restricted to an area limited by the radius provided by an extension cord.
The net result of the aforesaid lack of simple, effective means insuring uniform flow of parenteral fluids from a source thereof such as a suspended plastic bag has been that uniformity of flow is usually attempted to be attained by frequent visits of a nurse or nurses to the administration set to count the number of drops of the fluid flowing or being dispensed per minute or by the rate of emptying of a small reservoir made a part of the intravenous tubing.